Variable Transport Format Parameters for Fast Acknowledgment Feedback Mechanism

ABSTRACT

A first communication node ( 110 ) receives a stream of code blocks from a second communication node ( 120 ) over an acknowledged connection ( 131. ). The first communication node processes the received code blocks in accordance with at least one transport format parameter, TFP, detects errors in received code blocks, and transmits an acknowledgment in respect of groups of code blocks indicating whether at least one error was detected in the group. A first subset of the code blocks of a group are transmitted (e.g., modulated and demodulated) in accordance with a first TFP value, and a remainder of the code blocks are transmitted in accordance with a second TFP value. Because the first and second TFP values are independent, it is possible either to shorten the necessary processing time in the first communication node or, in connection with a predictive acknowledgment mechanism, to make the receiving-side processing of code blocks that do not contribute to the value of the transmitted acknowledgment more robust.

TECHNICAL FIELD

Disclosed herein are techniques for facilitating digital communicationover an error-prone connection between two communication nodes. Inparticular, there is proposed a predictive and a non-predictiveacknowledgment feedback mechanism for such a connection.

BACKGROUND

Wireless networks standardized by Third Generation Partnership Long TermEvolution (3GPP LTE) implement ARQ (Automatic Repeat Request) orhybrid-ARQ (HARQ), from which HARQ also includes forward errorcorrection. HARQ is used in HSDPA and HSUPA, which provide high-speeddata transmission for mobile phone networks such as UMTS, and in theIEEE 802.16-2005 standard for mobile broadband wireless access, alsoknown as “mobile WiMAX”. It is also used in EVDO and LTE wirelessnetworks.

In systems of this type, terminals are required to send acknowledgmentfeedback to the network indicative of a result of decoding a transportblock or codeword (ACK/NACK or ACK/NAK feedback). The ACK/NACK relatedto downlink transmissions is transmitted on the uplink. The feedback isused to trigger fast retransmissions. In LTE frequency-division duplex(FDD), as schematically depicted in FIG. 6, a terminal is required totransmit ARQ or hybrid-ARQ acknowledgment related to downlink subframe nin uplink subframe n+4. In FIG. 6, T_(P)denotes a propagation delay fromthe access node to the terminal; T_(TA) denotes an offset separating thestart of an uplink subframe relative to the start of a correspondingdownlink subframe at the terminal; T_(UE) is the processing timeavailable to the terminal; and T_(eNB)is the processing time availableto the access node. This allows the terminal between 2 and 3 ms fordecoding the transport block and preparing the uplink transmission thatcarries the ACK/NACK. The exact time depends on timing advance settings.

FIG. 7 illustrates a timing relationship between downlink data anduplink hybrid-ARQ acknowledgment for time-division duplex (TDD). Infact, the acknowledgment transmitted in uplink subframe 7 is bundled,and will be positively valued only if both of the downlink transmissionsin subframe 0 and 3 are correctly decoded.

In LTE, as outlined in FIG. 8, a transport block comprises one or morecode blocks. Each received code block needs to be correctly decoded,i.e. decoded without detected errors, in order for the transport blockto be deemed correctly decoded. A cyclic redundancy check (CRC) value isinserted into each code block. The CRC makes it possible for theterminal to determine whether it has been correctly decoded or not.

It is expected that future radio access (“5G”) transport blocks will bestructured in a similar way. For some services foreseen for 5G, however,the delay associated with ACK/NACK signaling as currently practiced inLTE will not be acceptable. More precisely, it is expected that the timeallowed for the terminal to decode a transport block and transmitACK/NACK feedback may be significantly reduced compared to LTE, possiblydown to tens of microseconds. In some proposed deployments of 5Gnetworks, terminals may be required to send ACK/NACK feedback to thenetwork before any further downlink or uplink signaling can take place.This means that the frame structure must leave sonic guard time to allowfor decoding of the transport block. In a typical implementation, thetime required to decode a code block once all its orthogonalfrequency-division multiplexing (OFDM) symbols have been receivedcorresponds approximately to the duration of one OFDM symbol. Guardtimes of this order of magnitude would be wasteful of system resources.It is therefore desirable to expedite the terminal's transmission ofACK/NACK feedback.

SUMMARY

In view of the state of the art outlined in the preceding section, theinvention proposes devices, methods, computer programs and computerprogram products, as defined by the independent claims.

A first communication node will be considered which is adapted foracknowledged connection to a second communication node and comprises atleast a receiver, at least one processor and a transmitter. Theconnection is a wireless or wired connection over a medium that is knownor expected to generate some amount of transmission errors or othererrors during normal operation. A purpose of an acknowledgment mechanismis to monitor and correct such errors. The first communication node islocated on a receiving side of the connection, in the sense that itreceives payload data. Certainly the first communication node alsotransmits data to the second communication, such as acknowledgments.Moreover, the acknowledged connection may be a full or partial duplexconnection, wherein payload data flows in both directions.

In the first communication node, the receiver is configured to receive apredefined group of code blocks from the second communication node. Toenable the first communication node to detect errors, either a checkvalue is associated with each code block or a check value is associatedwith each predefined group of code blocks. Referring to the firstoption, a code block in 3GPP LTE is the lowest level on which CRCinsertion can be performed. In this disclosure including the appendedclaims, “code block” denotes, for any communication system, the smallestunit that the system associates with an independent check value. It isnoted that the term “code block” is used in a forward-looking sense, toinclude also future equivalents, in particular, the smallest unitassociated with an independent check value in a 5G wirelesscommunication system, whether or not such unit is referred tospecifically as a “code block”. Sequential ordering of the code blocksis no essential feature of this invention; indeed, information from twoor more code block may be mapped to one modulation symbol in 3GPP LTE,so that arguably their respective transmission times areindistinguishable, and this fact is not expected to change in futureradio access technologies.

The at least one processor is configured, on the one hand, to processthe received code blocks in accordance with at least one transportformat parameter (TFP) and, on the other hand, to detect errors in thereceived code blocks using the check value or check values. When checkvalue insertion has been done on group level, then the at least oneprocessor performs error detection for an entire group of code blocks ata time. When check value insertion has been done on code block level,then the at least one processor performs error detection for one codeblock at a time and combines the error detection result into a totalerror for the group of code blocks. For instance, the firstcommunication node may be configured to transmit a negatively valuedacknowledgment for a predetermined group as soon as an error has beendetected for any the code blocks in the predefined group. If the atleast one processor produces error detection results e1, e2, e3, e4, e5,from which a positive value signifies the presence of an error, then theprocessor(s) may proceed to combine these as e1 OR e2 OR e3 OR e4 OR e5.This expression is positive as soon as one of the error detectionresults is positive.

The transmitter is configured to transmit to the second communicationnode an acknowledgment indicating whether at least one error wasdetected in said predefined group of code blocks, wherein a negativevalue of the acknowledgment signifies that an error was detected for thepredefined group or for at least one of the code blocks therein. Theinvention is applicable also in a network where acknowledgments areexchanged under the assumption that a positively valued acknowledgmentsignifies that the number of detected errors per predefined group isless than or equal to a pre-agreed threshold (e.g., 2, 3 or 4 errors),and a negatively valued acknowledgment signifies that the pre-agreedthreshold has been exceeded. The invention is furthermore applicable ina network where acknowledgments are exchanged under the assumption thata positively valued acknowledgment signifies that no errors or onlycorrigible errors have been detected, and a negatively valuedacknowledgment signifies that at least one non-corrigible error has beendetected.

The predefined groups may be defined in such manner that the transmitteris required or expected to transmit an acknowledgment for eachpredefined group, as may be laid down in a network standard or may bepre-agreed between the parties operating the first and secondcommunication nodes.

In one embodiment, the at least one processor is operable to apply afirst TFP value for a first subset of the code blocks of a predefinedgroup and a second TFP value for a remainder of the code blocks of thepredefined group. The first and second TFP values may be independent inthe sense that they need not be equal, but may be permitted to be equaltemporarily during operation of the first communication node. The firstand second TFP values may be independent in the sense that they aredifferent, yet without being required to be different at all times. Thefirst and second TFP values may be independent in the sense of beingindependently assignable. Furthermore, the embodiment encompasses acommunication node where the values are not required to be in aparticular numerical relationship to another, but may be allowed to bein such relationship to simplify an implementation or reduce signalingoverhead; for example, the first and second TFP values may be related bya constant multiplicative factor or by a constant additive offset. Thisembodiment also includes implementations where the values are signaledin a format where the first TFP value is encoded explicitly and thesecond is encoded in terms of its difference (or ratio) with respect tothe first TFP value.

A first communication node which is operable to apply different TFPvalues for different code blocks within a predefined group of codeblocks, as this embodiment provides, may be able to transmit theacknowledgment earlier than corresponding equipment according to thestate of the art. Indeed, for one or more code blocks that limit thetime required to transmit the acknowledgment, the TFP may either be setso as to shorten their processing time. Alternatively, if errordetection is done on a code block basis, the TFP for such code block(s)is set so as to make their processing more robust, reducing theirlikelihood of errors to such an extent that their error status need notcontribute to the substantive content of the acknowledgment; theacknowledgment may therefore be transmitted earlier than with availabletechnology. The fact these possible TFP modifications are not applied toall code blocks in a predefined group may help preserve the linkspectral efficiency.

As a possible further development within the scope of this embodiment,the at least one processor may be operable to apply a first TFP valuefor a first subset of the code blocks of a predefined group, a secondTFP value for a second subset of the code blocks of the predefinedgroup, and a third TFP value for a remainder of the code blocks of thepredefined group. In a case where N TFP values are used, the remainderis what is left after the first, second etc. up to the (N−1)^(th) subsetof code blocks have been removed from the predefined group of codeblocks. The remainder may alternatively be described as the complementof the union of the first subset and any second, third, fourth etc.subsets; this implies that the union of the remainder and all subsets isequal to the predefined group. The location of the remainder may beinitial or final in the predefined group, inside the predefined group ora union of disjoint sets of code blocks.

In another aspect, there is provided a method to be executed in a firstcommunication node for receiving a stream of code blocks from a secondcommunication node over an acknowledged connection. The methodcomprises: receiving a stream of code blocks from the secondcommunication node, wherein each code block or each predefined group ofcode blocks is associated with a check value enabling error detectionand belongs to a predefined group of code blocks; processing thereceived code blocks in accordance with at least one TFP; detectingerrors in received code blocks using the check value or check values;and transmitting to the second communication node an acknowledgment inrespect of each predefined group of code blocks, wherein a negativevalue of the acknowledgment signifies that an error was detected for atleast one of the code blocks in the predefined group. In an embodiment,the processing includes applying a first TFP value for a first subset ofthe code blocks of a predefined group and a second TFP value for aremainder of the code blocks of the predefined group, wherein the firstand second TFP values are independent.

Turning to the transmitting side, a second communication node adaptedfor acknowledged connection to a first communication node comprises atransmitter, a receiver and at least one processor.

In the second communication node, the at least one processor isconfigured to process the code blocks in accordance with at least oneTFP; to group the processed code blocks into predefined groups, andassociate each code block or each predefined group with at least onecheck value. It is noted that the check value may be inserted by the atleast one processor or may be present since the completion of upstreamprocessing steps.

The transmitter is configured to transmit the predefined groups the codeblocks.

The receiver is configured to receive from the first communication nodean acknowledgment in respect of one of the predefined groups oftransmitted code blocks. The receiver is furthermore configured to causethe transmitter to retransmit said predefined group of transmitted codeblocks in response to a received negatively valued acknowledgment.

In one embodiment, the at least one processor of the secondcommunication node is further configured to process a first subset ofthe code blocks of a predefined group in accordance. with a first TFPvalue and to process a remainder of the code blocks of the predefinedgroup in accordance with a second TFP value, which is independent of thefirst TFP value. As discussed above, the independence of the two or moreTFP values basically means that they are allowed to be different, thoughnot obliged to be always different during operation; alternatively, theyare allowed to be non-equal but also allowed to be temporarily equal.TFP values also remain “independent” in the sense of the appended claimseven if, in the interest of reducing signaling over-head, they arerelated by a constant factor or offset.

Because the at least one processor of the second communication nodeaccepts independent TFP values, the processing in die firstcommunication node is expedited in a way likely to accelerate itstransmission of the acknowledgment in respect of a predefined group ofcode blocks, as discussed above. The second communication node willbenefit from this in that it is likely to receive the acknowledgmentearlier than it would with available technology. This may reduce theaverage time that not yet acknowledged data needs to be buffered in thesecond communication node. Independently of the advantage in terms ofbuffer space use, a decrease in the average time to acknowledgment mayalso reduce the likelihood of the so-called window stall phenomenon. Aswill be further explained below, if the average acknowledgment time isreduced, fewer overhead need to be devoted to sequence numbering and/ora higher maximum stall-free data rate may be permitted. The fact that apotentially costlier TFP value need not be applied to all code blocks ina predefined group helps preserve link efficiency.

In another aspect, there is provided a method implemented in a firstcommunication node for transmitting a stream of code blocks to a firstcommunication node. The method comprises: processing the code blocks inaccordance with at least one transport format parameter, TFP; groupingthe processed code blocks into predefined groups and associating eachcode block or each predefined group of code blocks with a check value;transmitting the predefined groups of code blocks; receiving anacknowledgment in respect of one of the predefined groups of transmittedcode blocks, from the first communication node; and retransmitting saidpredefined group of transmitted code blocks if the acknowledgment isnegatively valued. In an embodiment, the processing includes applying afirst TFP value for a first subset of the code blocks of a predefinedgroup and applying a second TFP value for a remainder of the code blocksof the predefined group, wherein the first and second TFP values aredifferent.

In another aspect, there is provided method implemented in a secondcommunication node for transmitting a stream of code blocks to a firstcommunication node. The method comprises: processing the code blocks inaccordance with at least one transport format parameter, TFP; groupingthe processed code blocks into predefined groups and associating eachcode block or each predefined group of code blocks with a check value;transmitting the predefined groups of code blocks; receiving from thefirst communication node an acknowledgment in respect of one of thepredefined groups of transmitted code blocks; and in response to anegatively valued acknowledgment, retransmitting (505) said predefinedgroup of transmitted code blocks. In an embodiment, said processingincludes applying a first TFP value for a first subset of the codeblocks of a predefined group and applying a second TFT value for aremainder of the code blocks of the predefined group, wherein the firstand second TFP values are different.

In other aspects, there are also provided a computer program and acomputer-readable medium carrying this computer program.

It is noted the invention relates to all combinations of features, evenif recited in mutually different claims.

BRIEF DESCRIPTION OF THE DRAWING

Embodiments will now be described in greater detail and with referenceto the accompanying drawings, on which:

FIG. 1 illustrates a first and a second communication node communicatingover a wired or wireless acknowledged connection;

FIG. 2 illustrates a use case where an embodiment is implemented in anacknowledged connection between a wireless communication device (e.g.,terminal, mobile station, user equipment) and a wireless access node(e.g., base station, eNodeB);

FIG. 3 illustrates a use case where an embodiment is implemented in abackhaul link between two wireless access nodes (e.g., base stations,eNodeBs);

FIGS. 4 and 5 are flowcharts of a method in a (receiving) firstcommunication node and a (transmitting) second communication node,respectively;

FIGS. 6 and 7 are schematic timing diagrams illustrating hybrid-ARQ in3GPP LTE FDD and TDD, respectively;

FIG. 8 is an overview block diagram illustrating transport-channelprocessing in 3GPP LTE;

FIG. 9 illustrates three options for timing of acknowledgment feedbackin respect of a group of code blocks, according to embodiments disclosedherein, wherein periods of transmit processing time have been indicatedby dash-dotted line and periods of processing time at the receiver havebeen indicated by dashed line;

FIG. 10 illustrates processing of OFDM symbols (as exemplified byarrows) in a pipelining receiver running at full capacity, whereinnormally, transmit processing can only start one OFDM symbol durationafter complete receipt of the last OFDM symbol;

FIG. 11 illustrates processing in a receiver where TFPs in all codeblocks have been modified to make processing faster, so thatacknowledgment processing may start earlier than in FIG. 10;

FIG. 12 illustrates processing in a receiver where TEN in the last OFDMsymbol are modified to make processing faster, so that acknowledgmentprocessing may start earlier than in FIG. 10 while the link efficiencyis only marginally reduced;

FIG. 13 shows frequency allocations to a sequence of seven OFDM symbols,according to various embodiments, wherein (a) a processing time for thefinal OFDM symbol is reduced, (b) a different frequency allocation isapplied for the final OFDM symbol, (c) other TFPs than frequencyallocation are modified in the final OFDM symbol to achieve more robustprocessing, and (d) TFPs are modified for a part of an OFDM symbol, asmay be the case if TFP are assigned per code block, to reduce processingtime or increase robustness; and

FIGS. 14-17 illustrate how a first communication node according to anembodiment realizes one or more processing schemes (vertical axis) inresponse to different TIT values (horizontal axis).

DETAILED DESCRIPTION OF EMBODIMENTS

Within the context of the present disclosure, the term “communicationnetwork” or short “network” may particularly denote a collection ofnodes or entities, related transport links, and associated managementneeded for running a service, for example a telephony service or apacket transport service. Depending on the service, different node typesor entities may be utilized to realize the service. A network operatorowns the communication network and offers the implemented services toits subscribers. Typical examples of a communication network are radioaccess network (such as WLAN/Wi-Fi and cellular networks like 2G/GSM,3G/WCDMA, CDMA, LTE), mobile backhaul network, or core network such asIMS, CS Core, PS Core.

Within the context of the present disclosure, each of the term “userequipment” (UE) and “wireless communication device” refers to a devicefor instance used by a person for his or her personal communication. Itcan be a telephone-type of device, for example a telephone or a SIPphone, cellular telephone, a mobile station, cordless phone, or apersonal digital assistant type of device like laptop, notebook, notepadequipped with a wireless data connection. The UE may also be associatedwith non-humans like animals, plants, or even machines, and may then beconfigured for machine-type communication (MTC), which is also referredto as machine-to-machine (M2M) communication, device-to-device (D2D)communication or sidelink. A UE may be equipped with a SIM (SubscriberIdentity Module) comprising unique identities such as IMSI(International Mobile Subscriber Identity) and/or TMSI (Temporary MobileSubscriber Identity) associated with a subscriber using the UE. Thepresence of a SIM within a UE customizes the UE uniquely with asubscription of the subscriber.

Within the context of the present disclosure, each of the terms “basestation” and “wireless access node” refers to a node of a radio accessnetwork that is used as interface between land-based transport links andradio-based transport links, wherein the radio-based transport linkinterfaces directly with a UE. For example, in a GSM/2G access network abase station refers to a BTS, in a WCDMA/3G access network a basestation refers to a NodeB, and in a LTE access network a base stationrefers to a eNodeB. In WLAN/Wi-Fi architecture, a base station refers toan Access Point (AP).

The invention may be put to use in any node in a network that implementstransmitter or receiver functionality. One typical implementation is ina UE and relates to processing of a downlink transport blocks withACK/NACK feedback transmitted on uplink. Another implementation may bein multi-hop backhauling between network nodes, where fast feedback isessential.

FIG. 1 shows two communication nodes 10, 20 operable to becommunicatively connected by a wireless or wired connection, asindicated by the dashed line. The connection may be an acknowledgedconnection in the sense that some errors are monitored and thetransmitting side is configured to retransmit a predefined group of codeblocks in response to a request by the receiving side. The connectionmay as well comprise a retransmission protocol, such as a higher-layerretransmission protocol; one example, in LTE, is the Radio Link Control(RLC) protocol, through which may be requested retransmission of RLCprotocol data units, which are typically significantly larger than LTEcode blocks.

The first communication node 10 comprises a receiver 11 configured toreceive a predefined group of code blocks from the second communicationnode, wherein each code block or the predefined group of code blocks isassociated with a check value enabling error detection. Accordingly, thefirst communication node 10 is configured to operate for check valueinsertion on the level of a code block or a predefined group. Whilecheck value insertion may optionally be implemented on larger units thanthe predefined group of code blocks discussed here, the firstcommunication node 10 is preferably configured to disregard any checkvalues that are associated with smaller units than the code blocks. Thepredefined group comprises code blocks encoded by modulation symbols. Insome embodiments, the first communication node 10 may be configured toprocess predefined groups encoded by consecutive modulation symbols,such as OFDM symbols. It is noted that there is generally no stablenumerical relationship between modulation symbols and code blocks: itmay be envisioned that one code block is encoded by one or moremodulation symbols, and conversely, one modulation symbol may carry datafrom one or more code blocks.

The first communication node 10 further comprises at least one processor12, such as a single processor, a multi-core processor, a group ofcooperating processors, or processing circuitry. The at least oneprocessor 12 is configured to, on the one hand, process the receivedcode blocks in the predefined group in accordance with at least one TFP,and, on the other, to detect errors in the received code blocks usingthe check value or check values. The processing of the received codeblocks may include decoding symbols in the code blocks. The check valuemay be one of: a parity bit, a hash value, a checksum value, a cyclicredundancy check value, CRC value; for each of these examples, the errordetection may include recomputing the check value in an equivalentfashion as was done on the transmitting side (or equivalently, by analgorithm on which the communicating parties have agreed in advance) andassessing whether it is equal to the received check value. The errordetection may be an integrated stage of a demodulation process.

The first communication node 10 moreover comprises a transmitter 13configured to transmit to the second communication node 20, based onwhether errors were detected, an acknowledgment in respect of each ofsaid predefined groups of code blocks. For the purpose of thispresentation, it is agreed that a negative value of the acknowledgmentsignifies that an error was detected for at least one of the code blocksin the predefined group. The negative value of the acknowledgment mayhave the effect of triggering a retransmission. In the case where errorsare detected on code-block level check, a TRUE error detection resultmay denote, depending on the implementation, either that the concernedcode block was error free (agreement with the received check value) orcontained an error (disagreement with the received check value), andsimilarly, it is a matter of convention whether a TRUE value of acombination of error detection results denotes that all code blocks weredecoded satisfactorily or with one or more errors. Either way, it willbe within the abilities of one skilled in the art to identify a logicaloperation, such as OR, NOR, AND or NAND with two or more inputvariables, that provides the desired combined error detection result.

In an embodiment, the at least one processor 12 is operable to apply afirst TFP value for a first subset of the code blocks of a predefinedgroup and a second TFP value for a remainder of the code blocks of thepredefined group, wherein the first and second TFP values areindependent. The first and second TFP values applied by the at least oneprocessor 12 may be determined by information that the firstcommunication node 10 receives from the second communication node 20.For instance, the TFP values may be derivable from a property of thereceived code blocks. Alternatively or additionally, the first andsecond TFP values may be signaled separately. The TFP values may becontrolled at the transmitting end or decided at the receiving end. Forinstance, the first communication node 10 may be configured to apply aspecific TFP value to one or more final code block in a predefinedgroup. Alternatively, the first communication node 10 determines aproperty of the code block it receives, which then limits the number ofavailable processing options available for selection by the firstcommunication node 10. Further alternatively, at least one processor 12may be configured to determine at least the second TFP value on thebasis of statically or dynamically conveyed information indicating howmuch time is allowed for acknowledgment feedback, according to apredefined or pre-agreed rule, containing pairs of values of the timeallowed for acknowledgment feedback and corresponding second TFP values.

The many possible options for signaling the TFP values include thefollowing:

The receiver 11 receives an indication of a difference between the firstand second TFP values, and either the first or second TFP value isderivable from the received code blocks or from other signaling.

The receiver 11 retrieves the first and second TFP values from asemi-statically configured set of values, such as a set of values knownto the receiver 11 by higher-layer signaling, in particular RRCsignaling. The semi-statically configured set of values may beaccessible to both the first communication node 10 and the secondcommunication node 20.

The receiver 11 is configured to receive an indication of the first TFPvalue as downlink control information (DCI) from the secondcommunication node 20. The first TFP value is preferably indicatedexplicitly. As used herein, an explicit indication may mean that thereceiver 11 receives the TFP value itself or a reference to a look-uptable where it is found; values needing to be deducted from othersettings or that are incrementally coded may generally be characterizedas implicit rather than explicit.

In a variation of the preceding implementation, the first TFP value isin the DCI and the second TFP value is the first TFP value increased bya offset, such as a semi-statically configured offset.

In an alternative variation of the preceding implementation, the DCIfurther includes an indication of the second TFP value.

Envisioned are also combinations of the listed options.

As used in this disclosure, TFPs include one or more of the following:

parameters relevant to the modulation of data, including parameterswhich quantitatively or qualitatively describe the modulation;

code rate of a channel code;

code block size of a channel code;

channel code type;

OFDM symbol duration;

OFDM subcarrier bandwidth;

modulation order;

reference signal density;

power allocation;

multiple-input multiple-output (MEW) order or rank of transmission.

The at least one processor 12 may be configured to process a receivedcode block by realizing a processing scheme in accordance with the TFPvalue with which the code block is associated. In particular, the atleast one processor 12 may be configured to process a received codeblock by performing a processing scheme according to the TFP value withwhich the code block is associated. For each implementation, there existat least two different TFP values such that the realizations inaccordance with these TFP values are at least quantitatively differentfrom one another, possibly also qualitatively different.

FIGS. 14-17 schematically illustrate different examples how the at leastone processor 12 selects different realizations of a processing schemeor different processing schemes as a function of the TFP. In FIG. 14,points labeled on the horizontal axis represent values (scalars orvectors) of at least one discrete TFP, and points on the vertical axisrepresent different processing schemes selected in response to these. Itis noted that processing scheme P1 is selected both for TFP values A andB. The processing schemes P1, P2, P3 and P4 may follow a commonstructure in which some step or steps are added or omitted (e.g.,contributions from some frequency bands) or reordered, or arequantitatively modified by varying discrete or continuous numericalconstants acting on the data to be processed. Alternatively, theprocessing schemes P1, P2, P3 and P4 represent different processingapproaches, e.g., targeting channel code types requiring differentdemodulation, or involving different sequences of processing steps. InFIGS. 15-17, the horizontal axis represents a continuous TFP which takesvalues in an example interval [2.0, 2.81]. FIG. 15 illustrates the casewhere one processing scheme P1 is realized differently for differentvalues of the continuous TFP. It is generally true that the propertiesof two realizations of the processing scheme are more similar the closerthe TFP values are. Alternatively, as shown in FIG. 16, the at least oneprocessor 12 may realize a same processing scheme (e.g., P1) fordifferent values (e.g., 2.10, 2.11) of a TFP in a subrange; still the atleast one processor 12 is operable to accept TFP values in a range whereit realizes different processing schemes, such as processing schemes P1and P2 in different portions of the open interval (2.0, 2.5). FIG. 17illustrates a combination of what is shown in FIGS. 15 and 16, namelywhere successive subranges correspond, respectively, to a first constantsingle processing scheme P1, a variable single processing scheme P2(⋅)which is realized in a quantitatively variable manner reflecting thevalue of the TFP, and a second constant single processing scheme P3.

In embodiments, the realizations of the processing scheme(s) may differwith respect to

their probability of successful completion,

their necessary (or minimum) execution time, and/or

their cost, in the sense of how much resources they require in terms ofprocessing or memory space or both.

A meaningful comparison of the successful completion probability couldbe based on predefined, representative input data; the representativeinput data may contain errors, which represents a difficulty thatdifferent processing schemes, depending on their degree of algorithmicsophistication and/or allocated resources, have different chances ofovercoming. This makes it possible to expedite the processing in thefirst communication node in a way likely to accelerate its transmissionof the acknowledgment in respect of a predefined group of code blocks,according to one of the approaches outlined above, while preserving linkefficiency.

In particular, a predefined group of code blocks may be at leastpartially encoded by consecutive modulation symbols, such as an OFDMsymbol, precoded OFDM symbol, discrete-Fourier-transform-spread OFDM(DFTS-OFD) symbol, multicarrier symbol, precoded multicarrier symbol. Ina case where the code blocks are only partially encoded by consecutivemodulation symbols, they may be interrupted by reference signal symbols,as is common practice in LTE transmission; even in this case, at leastsome portion of the predefined group of code blocks is encoded by two ormore consecutive modulation symbols. Where the predefined group of codeblocks is at least partially encoded by consecutive modulation symbols,in the sense described, the at least one processor 12 is operable torealize the processing scheme in such mariner that a necessary executiontime for processing a modulation symbol is significantly less than theduration of a modulation symbol (i.e., such that a measurableimprovement results; or not approximately equal to the duration of amodulation symbol). It is common design practice to allocate processingresources with the aim that the necessary execution time for processinga modulation symbol approximately equals the duration of a modulationsymbol. Indeed, allowing the processing time to exceed the duration ofone symbol may lead to queues and poor resiliency, while the conversemay represent uneconomical use of the processing resources if applied toall symbols. In general, it is possible to process data corresponding toa modulation symbol in significantly less time than the duration of amodulation symbol by allocating more processing resources for theprocessing of this data. In this embodiment, if the ability of at leastone processor 12 to process a modulation symbol significantly fasterthan the duration of the symbol is applied to one or more of the finalsymbols in a predefined group, then the first communication node 10 willbe able to transmit the acknowledgment earlier than a correspondingcommunication node according to the state of the art. If additionallysuch accelerated processing mode is applied only to the final symbol orsymbols, the acceleration will not consume a significant amount ofresources.

In a first group of embodiments, the at least one processor 12 of thefirst communication node 10 may be configured to detect errors on aper-code-block basis. The at least one processor 12 is furtherconfigured to accept a predefined group where the first subset (asdefined by the assignment of TFP values) does not include the one ormore code block which are most recent. Reference is made to the codeblock or code blocks that were transmitted by the second communicationnode 20 most recently, as evidenced by sequence numbers or the like,preferably not by the time of successful receipt at the firstcommunication node 10, which may not reflect the time of an originaltransmission. In embodiments within this group, the transmitter 13 isconfigured to transmit an acknowledgment for the predefined group whichis independent of any error detection results for said most recent codeblock or code blocks. The communicating parties operating the first andsecond communication nodes 10, 20 have typically agreed, e.g., byadhering to an industry standard such as 3GPP LTE, on a format fortransmitting the acknowledgment. In such a standardized format, it mayhave been supposed or implicitly supposed that the acknowledgment for apredefined group of two or more code blocks be based on a combination oferror detection results for all code blocks in the predefined group. Inan embodiment, the acknowledgment may be sent in the agreed format eventhough it is based on a combination of error detection results for asubset of the code blocks in the predefined group. In particular, anegatively valued acknowledgment in respect of a predefined group ofcode blocks may be transmitted in the form of a request forretransmission of that predefined group of code blocks. Accordingly,this embodiment may be implemented on the receiving side unnoticeably tothe transmitting side; this provides for easily achievable compatibilitywith legacy equipment.

It is noted that, even if the first communication node 10 transmits apositively valued acknowledgment that turns out to be factuallyincorrect (i.e., the error detection results missing from thecombination are such that they would have led to a negative value of theacknowledgment), then a retransmission protocol operating independentlyof the acknowledgment feedback at the focus of this disclosure mayensure that the incorrectly or unsuccessfully decoded data willeventually become available to the first communication node 10.

FIG. 9 shows an example in the context of LTE, wherein a code block maybe referred to precisely as “code block” and a predefined group of codeblocks may be referred to as a “transport block”. The invention isapplicable to any communication system where a transport block consistsof multiple code blocks or frames. In FIG. 9 is shown a transport blockcomprising K=5 code blocks (“CB”) encoded by N=7 OFDM consecutivesymbols, which are arranged with respect to a horizontal time axisindicating their respective times of receipt. A solid rectanglecorresponding to the duration of one OFDM symbol is shown to the rightof the last OFDM symbol. No transmission time is associated with a codeblock as such, but an adjacent dashed rectangle to the right of eachcode block area illustrates the time interval in which the receivingside processes a code block, including error detection for that codeblock.

Immediately above the time axis, three possible time periods forpreparing and transmitting an acknowledgment in respect of the transportblock are indicated. Transmit processing time is understood as the timerequired from the availability of ACK/NACK feedback information in theUE until the part of the feedback message that depends on the ACK/NACKfeedback is ready for transmission. Accordingly, the beginning of eachtime period refers to initiation of the acknowledgment transmission,which may include one or more of the following: populating a feedbackmessage template with the value of the acknowledgment, retrievingsupplementary information to accompany acknowledgment, initiatingprocessing to generate such supplementary information, ensuringcompliance with an agreed message format, or the like. This means thatthe first communication node 10 may perform sonic actions before theillustrated transmit processing time starts: begin building a feedbackmessage, retrieve supplementary information to accompany acknowledgment,generate supplementary information and the like. It is furthermoreunderstood that the end of each illustrated time period refers tostarting the generation of an electromagnetic waveform that carries theacknowledgment. As such, the transmission stricto sensu is contained ina time period (not shown) immediately succeeding the illustratedtransmit processing time.

In an embodiment illustrated in FIG. 9 as option 1, transmit processingstarts after the last OFDM symbol is received but before the last codeblock has been decoded (dashed rectangle). The associated ACK/NACKfeedback refers to the full transport block (“predefined group”), but isbased only on code block 1, 2, 3 and 4 (or more generally, on the codeblocks in the range [1, K-P] with P=1). In this option, even though allcode blocks are eventually decoded, only code blocks that are mapped tothe M=6 first OFDM symbols are used for the ACK/NACK feedback.Generalizing this teaching into cases where the last symbol does notencode a single code block, an acknowledgment for the predefined groupmay be based on a combination of error detection results for all butthose code blocks which are at least partially encoded by the final OFDMsymbol in the sequence. Using the notation from above, one sets M=N−1.The duration of one OFDM symbol may be of the order 50-100 μs in anavailable wireless communication system in view of transmit processingtime, guard time and receiver processing time. With reference again tothe case P=1, if code block 5 is associated with a TFP value that givesit increased robustness compared to the K-P first code blocks, then theprediction is likely to be more accurate and robust. Put differently,the TFP value associated with block 5 causes the at least one processor12 to realize a processing scheme that has relatively higher robustnessthan what is used for earlier code blocks. The at least one processor 12may be configured to process the first subset and the remainder usingrespective realizations of a processing scheme that differ with respectto robustness. As an alternative or addition to this, the TFPs of thelast OFDM symbol can be set to enable higher robustness. Theresponsibility for determining the TFP values may be located on thetransmitting side, such as the second communication node 20. Typicallythe first communication node 10 may notice that different code blocks orOFDM symbols are associated with different TFP values—in someimplementations this may in fact be necessary to ensure correctprocessing on the receiving side—but may not be aware of the reason whythe values have been set in this way.

As regards future communication systems, such as 5G, the inventors haverealized that it may be advantageous to base an acknowledgment for apredefined group of code blocks on a combination of error detectionresults for all but those code blocks which are at least partiallyencoded by the final modulation symbol. This is because the duration ofa modulation symbol is likely to be set in view of the processing timesand guard time, whereby scaling divergence is avoided.

Still with reference to FIG. 9, option 1, the value of theacknowledgment depends only on error detection results for code blocksbelonging to the first subset. The acknowledgment is preferablyindependent of any error detection results for the code blocks belongingto the remainder of the predefined group. It is not essential thaterrors be detected for the code blocks in the reminder of the predefinedgroup. Possibly, and as may be unnoticeable to the first communicationnode 10, the second TFP value (applying to the remainder) is set in suchmanner as to make its processing more error robust. This justifies anassumption that the error probability for the code blocks in theremainder is bounded above by (i.e., is always less than or equal to)the error probability for the code blocks in the first subset. Based onthis assumption, if the error status of the first subset is used as anindicator for the error status of the remainder, it is unlikely toproduce false positive values.

In an embodiment illustrated in FIG. 9 as option 2, transmit processingstarts before the last OFDM symbol is received. In this example, all butthe last two code blocks are decoded. The associated ACK/NACK feedbacktransmission refers to the full transport block, but is based only oncode blocks 1, 2 and 3 (P=2). In this option, only code blocks that aremapped to the first M=5 OFDM symbols are used for the ACK/NACK feedback.Still in an example where P=2, if code blocks 4 and 5 (“remainder”) areassociated with TFP values that give them increased robustness comparedto code blocks 1, 2, . . . , K-P (“first subset”), then the predictionis likely be more accurate and robust. Additionally or alternatively,the TFPs of the last two OFDM symbols may be set to enable higherrobustness.

It is a common trait of the embodiments illustrated as options 1 and 2that transmission of the acknowledgment is initiated before the firstcommunication node 10 has completed detection of errors in all codeblocks in the predefined group. In particular, transmission of theacknowledgment is initiated before the at least one processor 12 hascompleted error detection on at least one code block outside saidsubset. In a variation to the embodiments illustrated as options 1 and2, the first communication node 10 may base the acknowledgment on errordetection results for code blocks that are non-consecutive; this is tosay, the “first subset” is a collection of non-consecutive code blocks.It can furthermore be envisioned to base the acknowledgment on errordetection results for code blocks that are non-initial in the predefinedgroup of code blocks. Further still, the acknowledgment may be based onan irregular sequence, such as code blocks 1, 3 and 4 in the case N=5.Especially if the error detection is separate from the decodingprocessing, such exclusion of some non-endpoint code blocks mayrepresent a reduction of the processing load. Since consecutive codeblocks are strongly correlated, as the inventors have realized,excluding some non-endpoint code blocks only reduces the reliability bya negligible amount.

There may be a tradeoff associated with the embodiments illustrated asoptions 1 and 2 in FIG. 9. If too few code block are used for ACK/NACKfeedback, then the risk of sending an ACK for a transport block thatdoes in fact fail to decode (due to decoding of one of the last codeblocks failing) increases. If too many code blocks are included, thenguard time is unnecessarily long. Finding a suitable balance betweenthese extreme conditions is believed to be within the abilities of oneskilled in the art who has studied the present disclosure. As alreadyintimated, the probability of a failure may be advantageously reduced ifthe one or more most recent code blocks, which do not influence thevalue of the acknowledgment, are associated with a TFP value causing theat least one processor 12 to realize the processing scheme withrelatively higher robustness; for instance, the one or more most recentcode blocks may be placed in the “remainder” of the predefined group andthe associated “second TFP value” is one leading to such increasedrobustness.

How much earlier the acknowledgment is transmitted depends on how muchback-off of the TFPs is performed. The cost in terms of link spectralefficiency also depends on the back-off of the TFPs. In a TDD system orhalf-duplex FDD systems, uplink transmission can only start after thedownlink transport block has been received. It is furthermore commonpractice to separate downlink reception and uplink transmission by aguard period (or guard time), mainly in order to reduce interference atthe base station. The guard period may be included also where the uplinktransmission is subject to a terminal-specific timing advance, as isparticularly important in cells with large extent. In LTE, the guardperiod is at least the duration of one OFDM symbol. This places a limiton how early the acknowledgment can be transmitted. With reasonableassumptions on transmit processing time, guard time and processing timeat the receiver, an advantageous choice may be M=N−1 (or P=1), that is,any code block that is mapped to the last OFDM symbol does notcontribute the value of the acknowledgment.

It is finally noted that sonic features of the first group ofembodiments have been discussed in detail in the applicant's co-pendingInternational application PCT/SE2016/050150, in particular FIG. 9therein together with corresponding sections of the description, whichis hereby included by reference.

A second group of embodiments, illustrated in FIG. 9 as option 3, can beimplemented both in a first communication node 10 where the at least oneprocessor 12 is adapted to detect errors on the level of separate codeblocks and in a first communication node 10 where the at least oneprocessor 12 is configured to detect errors on the level of a predefinedgroup. In the first case, the at least one processor 12 uses checkvalues associated with code blocks as input, whereas in the second case,it uses check values associated with the predefined group of code blocksas a whole. In this group of embodiments, transmit processing beginsafter all code blocks in the downlink transmission have been receivedand decoded. The ACK/NACK feedback related to the predefined group ofcode block then is based on all code blocks. To expedite the sending ofthe acknowledgment, the first subset is selected so as not to includethe most recent code block or code blocks in the predefined group, andthe at least one processor 12 is configured to process the first subsetand the remainder using respective realizations of a processing schemethat differ with respect to necessary execution time.

In this disclosure, “necessary execution time” may be understood asspecific necessary execution time or necessary execution time permodulation symbol, e.g., the time needed to process a received OFDMsymbol. Execution time may be based on a complexity analysis (orrun-time complexity) of a representative algorithm in the processingscheme or alternatively on simulations of the processing scheme oractual measurements on the processing scheme executing. A comparison ofthe execution time for two different realizations of the processing ortwo different processing schemes-may neither require a completecomplexity analysis nor measurements: it may be sufficient to determinewhether a costly processing step is present in one and absent in theother, or if a relatively more costly processing step in one issubstituted for a relatively less costly processing step in the other.In this connection, cost mainly refers to computational cost ornecessary processing time, and to some extent to use of memory space.

The processing scheme may execute in less time because the encoding isless involved. Alternatively, it may be possible to apply a simpler andthus faster realization of the processing scheme—or a qualitativelydifferent processing scheme—because the robustness of the encoding is somuch higher. Put differently, this alternative allows using a processingscheme that is in itself more error-prone, because the encoding it actson is less error-prone.

Advantageously, the most recent code block or code blocks are processedusing a faster realization of the processing scheme, or using aprocessing scheme which is faster than the processing scheme that isused for the first subset, i.e., the less recent potion of thepredefined group of code blocks.

The embodiment is further explained with reference to FIGS. 10 and 12.For reference purposes, FIG. 10 illustrates processing of OFDM symbols(as exemplified by arrows) in a pipelining receiver running at fullcapacity wherein, normally, transmit processing can only start one OFDMsymbol duration after complete receipt of the last OFDM symbol. FIG. 11illustrates processing in a receiver where TFPs in all code blocks havebeen modified to make processing faster, so that acknowledgmentprocessing may start earlier than in FIG. 10; this may however be acostly way of accelerating the acknowledgment. FIG. 12 illustratesprocessing in a receiver where TFPs in the last OFDM symbol are modifiedto make processing faster, so that acknowledgment processing may startearlier than in FIG. 10 while the link efficiency is only marginallyreduced.

Common to both groups of embodiments, FIG. 13 illustrates how differentTFPs may be varied in order to expedite the acknowledgment for apredefined group of code blocks. Seven consecutive OFDM symbols thatcarry a LTE-type transport block are represented by rectangles. Thevertical extent of a rectangle represents what frequencies are allocatedto its transmission, and its horizontal extent represents the timeduration of different OFDM symbols. In a), the duration of the finalOFDM symbol is reduced by selecting its TFP value accordingly. In b), adifferent frequency allocation, which is an example of a TFP, is appliedfor the final OFDM symbol, whereas this symbol may have the sameduration as the initial symbols in the predefined group. In c), assuggested by the different hashing pattern, a different TFP thanfrequency allocation is modified in the final OFDM symbol to achievemore robust processing. Finally in d), TFPs are modified for a part ofan OFDM symbol, as may be the case if TFP are assigned per code block,to reduce processing time or increase robustness. It is clear in each ofa) to d) that the acknowledgment may be transmitted earlier than withavailable technology, so that the guard time can be advantageouslyreduced.

FIG. 2 shows a portion of a wireless network including a core network130, a base station 120 and a UE 110. The base station 120 is connectedover a wired (or fixed) connection 132 to the core network 230 and overa wireless downlink connection 131 to the UE 110. Both connections 131,132 may be error-prone to some extent and may benefit from the teachingsdisclosed herein. In an embodiment, the UE 110 performs error detectionon code blocks received over the downlink connection 131 and sendsacknowledgments to the base station 120 on an uplink (not shown),wherein one TFP value is applied for some code blocks in a predefinedgroup and an independent TFP value is applied for a remainder of thecode blocks in the predefined group.

FIG. 3 shows a portion of a wireless network including a core network230, a first and second base station 240, 220 and a UE 210. The firstbase station 240 is connected over a wired (or fixed) connection 233 tothe core network 230 and over a backhaul connection 232 to the secondbase station 220. The second base station 220 is in turn connectedwirelessly to the UE 210, and thereby acts as a relay. All threeconnections 231, 232, 233 may be error-prone to some extent and maybenefit from the teachings disclosed herein. In an embodiment, thesecond base station 220 performs error detection on code blocks receivedover the backhaul connection 232 and sends acknowledgments to the firstbase station 240, wherein one TFP value is applied for some code blocksin a predefined group and an independent TFP value is applied for aremainder of the code blocks in the predefined group.

The wireless networks discussed with reference to FIGS. 2 and 3 may becellular networks, such as LTE (including LTE-Advanced) or a 5G wirelessnetwork. Each of the wireless connections 131, 231, 232 may be atime-division duplex (TDD) connection, a full frequency-division duplex(FDD) or half-duplex FDD connection, a proper full duplex connection.

In the case of an LTE network, the predefined group of code blocks maybe referred to as a transport block. In a 5G or younger wirelesscommunication system, the phrase “predefined group of block” may need tobe reinterpreted in view of a possible change of the term “code block”,as already discussed. Whether or not such reinterpretation is necessaryin future communication technologies, the “predefined group” is to beunderstood as a unit which the receiving side is required (e.g., throughagreement, standardization or the like) to acknowledge independently,and typically within a predefined time after transmission. Embodimentsdisclosed herein teach that in such a “predefined group”, one TFP valueis applied for some code blocks and an independent. TFP value is appliedfor a remainder of the code blocks therein.

In the case of an LTE network, alternatively or additionally, theacknowledgment may be transmitted on a physical uplink control channel,PUCCH.

The operation of the first communication node 10 may be summarized bythe method 400 illustrated in FIG. 4. The method 400 comprises a firststep 401 of receiving a stream of code blocks from the secondcommunication node, wherein each code block or each predefined group ofcode blocks is associated with a check value enabling error detectionand belongs to a predefined group of code blocks. The method 400 furthercomprises a second step 402 of processing the received code blocks inaccordance with at least one TFP; a third step 403 of detecting errorsin received code blocks using the check value or check values; and afourth step 404 of transmitting to the second communication node anacknowledgment in respect of each predefined group of code blocks,wherein a negative value of the acknowledgment signifies that an errorwas detected for at least one of the code blocks in the predefinedgroup. In an embodiment, the second step 402 includes applying a firstTFP value for a first subset of the code blocks of a predefined groupand a second TFP value for a remainder of the code blocks of thepredefined group, wherein the first and second TFP values areindependent in the sense discussed above; in particular the first andsecond TFP values may be different.

Resuming the description of FIG. 1, the second communication node 20 isadapted for transmitting a stream of code blocks over a connection,which may be an acknowledged connection in the sense discussed above, tothe first communication node 10. The second communication node 20comprises at least one processor 21, a transmitter 22 and a receiver 23.The at least one processor 21, which may be implemented as a singleprocessor, a multi-core processor, a group of cooperating processors, orprocessing circuitry, is configured to process the code blocks inaccordance with at least one TFP. Example processing steps are shown inFIG. 8. As exemplified above, the TFPs may affect modulation, coding andtransmission and therefore typically affect both the transmitting andreceiving sides, that is, both the first 10 and second 20 communicationnodes. The at least one processor 21 is further configured to group theprocessed code blocks into predefined groups and associate each codeblock with at least one check value; alternatively, it is furtherconfigured to associated each predefine group with at least one checkvalue. The transmitter 22 is configured to transmit the predefinedgroups of code blocks. The receiver 23 is configured to receive anacknowledgment from the first communication node, wherein theacknowledgment concerns one of the predefined groups of transmitted codeblocks. If the receiver 23 determines that the received acknowledgmentis negatively valued, it causes the concerned predefined group oftransmitted code blocks to be retransmitted, or retransmits thepredefined group of transmitted code blocks. For this purpose, thesecond communication node 20 may further comprise a buffer shown) fortemporarily storing transmitted code blocks or data carried bytransmitted code blocks. In normal operation, the content of the bufferis deleted or marked as allowed to be deleted or overwritten once it hasbeen positively acknowledged from the receiving side. In an embodiment,the at least one processor 21 is further configured to process a firstsubset of the code blocks of a predefined group in accordance with afirst TFP value and to process a remainder of the code blocks of thepredefined group in accordance with a second TFP value. The first andsecond TFP values are independent in the sense that they are allowed tobe different; preferably, they may also assume equal values in limitedperiods of time.

The at least one processor 21 of the second communication node 20accepts using or applying independent TFP values when processing codeblocks and the corresponding processing in the first communication node10 is performed in accordance with these TFP values. As such, the secondcommunication 20 influences the first communication node 10 in a mannerlikely to accelerate its transmission of the acknowledgment in respectof a predefined group of code blocks, as discussed above. The secondcommunication node 20 may benefit from accelerated acknowledgment byreceiving the acknowledgment earlier than it would with availabletechnology. This may reduce the average time that not yet acknowledgeddata needs to be buffered in the second communication node, and soreduces the need for buffering, i.e., the necessary for memory space.Independently of the buffering-related advantage, a decrease in theaverage time to acknowledgment may also reduce the likelihood of theso-called window stall phenomenon, wherein a limited availability ofprotocol data unit (PDU) sequence numbers compels a transmitting side towithhold data until some of the transmitted PDUs have been acknowledgedand, as a result, their sequence numbers released. If the average timebetween a transmission and a (positive) acknowledgment of thetransmitted data is relatively smaller, the size of the PDU sequencenumber space will have a relatively less limiting influence on themaximum stall-free transmission rate. This may imply that fewer PDUheader bits may be devoted to the PDU sequence number. The fact that apotentially costlier TFP value need not be applied to all code blocks ina predefined group helps preserve link efficiency.

In an embodiment, the second communication node 20 may be configured toassign the first and second TFP values such that the correspondingprocessing (i.e., processing in the first communication node 10, such asdecoding symbols in the code blocks) of a code block associated with thesecond TIT value has a relatively higher probability of success than thecorresponding processing of a code block associated with the first TFPvalue. This will increase the reliability of a predictiveacknowledgment, i.e., one that the first communication node 10 generatesindependently of the error detection status of code blocks belonging tothe remainder of the predefined group of code blocks. This has beendisclosed above as the first group of embodiments on the receiving side.The increased reliability may meant that the predictive acknowledgmentproduces relatively fewer false positive values.

In an embodiment, the second communication node 20 may be configured toassign the first and second TFP values such that the correspondingprocessing (i.e., processing in the first communication node 10) of acode block associated with the second TFP value has a relatively shorternecessary execution time than the corresponding processing of a codeblock associated with the first TFP value. In a first communication node10 configured to transmit an acknowledgment that is based on acombination of the error detection status of all code blocks in apredefined group, this is likely to reduce the time elapsing fromreceipt of data to transmission of a corresponding acknowledgment. Thishas been disclosed above as the second group of embodiments on thereceiving side. Preferably, necessary processing time for the second TFPvalue is significantly less than the duration of one modulation symbol.

In an embodiment, the first subset does not include (i.e., is short of)the P≥1 code blocks in the predefined group which are most recent in thestream of code blocks. Assigning a special TFP value (“second TFPvalue”) to these code blocks, which may bring about a higher cost, maybe particularly advantageous in that these code blocks will normally beprocessed last in order in the first communication node 10. This isreasonable both in the case of predictive acknowledgment, where the mostrecent code blocks cannot directly trigger a retransmission, and in thecase of deterministic acknowledgment, where the processing of the mostrecent code blocks delay the completion of the acknowledgment and hencedelay the time at which they it is transmitted to the secondcommunication node 20. In a further development, the secondcommunication node 20 is configured to adapt the number P in response toone or more of the following factors:

the size of the code blocks in the predefined group;

the number of code blocks that the predefined group comprises;

is the content of statically conveyed information regarding a timeallowed for acknowledgment feedback;

the content of dynamically conveyed information regarding a time allowedfor acknowledgment feedback;

an active acknowledgment feedback timing mode that has been selectedfrom a plurality of selectable acknowledgment feedback timing modes andis currently valid;

current timing advance settings, which may be determined by the secondcommunication node 20 if this is acting as base station in a cellularsystem and which may affect the link budget.

Example ways in which the TFP values may be signaled from the secondcommunication node 20 to the first communication node 10 have beendiscussed in detail above, including the option of using DCI for thispurpose and various incremental formats.

The operation of the second communication node 20 may be summarized bythe method 500 illustrated in FIG. 5. The method 500 comprises a firststep 501 of processing the code blocks in accordance with at least oneTFP and a second step 502 of grouping-unless this has been done inupstream processing steps-the processed code blocks into predefinedgroups and associating each code block or each predefined group of codeblocks with a check value. The method 500 further comprises a third step503 of transmitting the predefined groups of code blocks; a fourth step504 in which the second communication node 20 receives an acknowledgmentin respect of one of the predefined groups of transmitted code blocksfrom the first communication node 10; and a fifth step 505 where thesecond communication node 20 retransmits the predefined group oftransmitted code blocks. In an embodiment, the first step 501 includesapplying a first TFP value when processing a first subset of the codeblocks of a predefined group and applying a second TFP value whenprocessing a remainder of the code blocks of the predefined group. Thefirst and second TFP values are independent in the sense discussedinitially; in particular they may be different.

Embodiments herein also include a computer program comprisinginstructions which, when executed by at least one processor of a first10 or second 20 communication node, cause the communication node tocarry out the methods shown in FIGS. 4 and 5, respectively, orvariations thereof. In one or more embodiments, a carrier containing thecomputer program is one of communication media (or transitory media,such as an electronic signal, optical signal, radio signal) or computerreadable storage media (or non-transitory media). The term computerstorage media includes both volatile and nonvolatile, removable andnon-removable media implemented in any method or technology for storageof information; computer storage media includes but is not limited toRAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM,digital versatile disks or other optical disk storage, magneticcassettes, magnetic tape, magnetic disk storage or other magneticstorage devices, or any other medium which stores the desiredinformation and is accessible by a computer. In at least one embodiment,a communication node or other apparatus is configured to perform theoperations or functions disclosed herein, based at least in part on nodeprocessing circuitry executing computer program instructions stored in anon-transitory computer-readable medium.

The present invention may, of course, be carried out in other ways thanthose specifically set forth herein without departing from essentialcharacteristics of the invention. The present embodiments are to beconsidered in all respects as illustrative and not restrictive, and allchanges coming within the meaning and equivalency range of the appendedclaims are intended to be embraced therein.

1-39. (canceled)
 40. A first communication node for receiving codeblocks over an acknowledged connection to a second communication node,comprising: a receiver configured to receive a predefined group of codeblocks from the second communication node, wherein each code block orthe predefined group of code blocks is associated with a check valueenabling error detection; processing circuitry configured to: processthe received code blocks in accordance with at least one transportformat parameter (TFP); and detect errors in the received code blocksusing the check value or check values; and a transmitter configured totransmit to the second communication node an acknowledgment indicatingwhether at least one error was detected in the predefined group, whereinthe processing circuitry is configured to apply a first TFP value for afirst subset of the code blocks of a predefined group and a second TFPvalue for a remainder of the code blocks of the predefined group,wherein the first and second TFP values are independent.
 41. The firstcommunication node of claim 40, wherein the processing circuitry isconfigured to process a received code block by realizing a processingscheme in accordance with a TFP value associated with the received codeblock, wherein the processing circuitry is operable to accept a TFPrange across which realizations are at least quantitatively different.42. The first communication node of claim 41, wherein realizations ofthe processing scheme in accordance with distinct TFP values differ withrespect to one or more of: probability of successful completion;necessary execution time; and necessary processing or memory resources.43. The first communication node of claim 42, wherein: a predefinedgroup of code blocks comprises code blocks at least partially encoded byconsecutive modulation symbols; and the processing circuitry isconfigured to realize the processing scheme in such manner that anecessary execution time for processing a modulation symbol is less thanthe duration of a modulation symbol.
 44. The first communication node ofclaim 40, wherein: the processing circuitry is configured to detecterrors on a per-code-block basis; the first subset does not include theP≥1 most recent code blocks in the predefined group; and the transmitteris configured to transmit an acknowledgment for the predefined groupwhich is independent of any error detection results for said most recentcode blocks.
 45. The first communication node of claim 44, wherein thetransmitter is configured to initiate transmission of the acknowledgmentbefore the processing circuitry has completed detection of errors in allcode blocks in the predefined group.
 46. The first communication node ofclaim 40, wherein: the first subset does not include the P≥1 most recentcode blocks in the predefined group; the processing circuitry isconfigured to process the first subset and the remainder usingrespective realizations of a processing scheme that differ with respectto necessary execution time; and the transmitter is configured totransmit an acknowledgment for the predefined group which is based on acombination of error detection results for all code blocks of thepredefined group.
 47. The first communication node of claim 40, whereinthe acknowledged connection to the second communication furthercomprises a retransmission protocol.
 48. The first communication node ofclaim 40, wherein the first communication node is a user equipment, thesecond communication node is a base station and the acknowledgedconnection is a downlink.
 49. The first communication node of claim 40,wherein the first and second communication nodes are base stations andthe acknowledged connection is a wireless backhaul link or a relay link.50. The first communication node of claim 40, wherein the first andsecond communication nodes are user equipments and the acknowledgedconnection is a sidelink.
 51. The first communication node of claim 40,wherein the at least one TFP is one or more of the following: parametersrelevant to the modulation of data; code rate of a channel code; codeblock size of a channel code; channel code type; orthogonalfrequency-division modulation (OFDM) symbol duration; OFDM subcarrierbandwidth; modulation order; reference signal density; power allocation;and MIMO order or rank of transmission.
 52. A second communication nodefor transmitting a stream of code blocks over an acknowledged connectionto a first communication node, comprising: processing circuitryconfigured to process the code blocks in accordance with at least onetransport format parameter (TFP), group the processed code blocks intopredefined groups and associate each code block or each predefined groupwith at least one check value; a transmitter configured to transmit thepredefined groups of code blocks; and a receiver configured to: receivefrom the first communication node an acknowledgment in respect of one ofthe predefined groups of transmitted code blocks; and causeretransmission of said predefined group of transmitted code blocks inresponse to a negatively valued acknowledgment, wherein the processingcircuitry is configured to process a first subset of the code blocks ofa predefined group in accordance with a first TFP value and to process aremainder of the code blocks of the predefined group in accordance witha second TFP value, which is independent of the first TFP value.
 53. Thesecond communication node of claim 52, wherein the processing circuitryis configured to select the second TFP value such that correspondingprocessing of a code block in the first communication node has arelatively higher probability of success with the second TFP value thanwith the first TFP value.
 54. The second communication node of claim 52,wherein the processing circuitry is configured to select the second TFPvalue such that a necessary execution time for corresponding processingof a code block in the first communication node is relatively shorterwith the second TFP value than with the first TFP value.
 55. The secondcommunication node of claim 54, wherein: the predefined group comprisescode blocks at least partially encoded by consecutive modulationsymbols; and the necessary execution time for corresponding processingof a modulation symbol is less than the duration of a modulation symbolwith the second TFP value.
 56. The second communication node of 52,whose cost of one or more of processing a code block and transmittingthe code block differs between the first and second TFP values.
 57. Thesecond communication node of 52, wherein the first subset does notinclude the P≥1 code blocks in the predefined group which are mostrecent in the stream of code blocks.
 58. The second communication nodeof claim 57, wherein the processing circuitry is configured to adapt thenumber P in response to one or more of the following factors: size ofthe code blocks in the predefined group; number of code blocks in thepredefined group; statically conveyed information on time allowed foracknowledgment feedback; dynamically conveyed information on timeallowed for acknowledgment feedback; an active acknowledgment feedbacktiming mode of a plurality of selectable acknowledgment feedback timingmodes; and current timing advance settings.
 59. The second communicationnode of claim 52, wherein the first communication node is a userequipment, the second communication node is a base station and theacknowledged connection is a downlink.
 60. The second communication nodeof claim 52, wherein the first and second communication nodes are basestations and the acknowledged connection is a wireless backhaul link ora relay link.
 61. The second communication node of claim 52, wherein thefirst and second communication nodes are user equipments and theacknowledged connection is a sidelink.
 62. The second communication nodeof claim 52, wherein the at least one TFP is one or more of thefollowing: parameters relevant to the modulation of data; code rate of achannel code; code block size of a channel code; channel code type;orthogonal frequency-division modulation (OFDM) symbol duration; OFDMsubcarrier bandwidth; modulation order; reference signal density; powerallocation; and MIMO order or rank of transmission.
 63. A methodimplemented in a first communication node for receiving a stream of codeblocks from a second communication node, comprising: receiving a streamof code blocks from the second communication node, wherein each codeblock or each predefined group of code blocks is associated with a checkvalue enabling error detection and belongs to a predefined group of codeblocks; processing the received code blocks in accordance with at leastone transport format parameter (TFP); detecting errors in received codeblocks using the check value or check values; and transmitting to thesecond communication node an acknowledgment in respect of eachpredefined group of code blocks, wherein the acknowledgment indicateswhether at least one error was detected in the predefined group, whereinsaid processing includes applying a first TFP value for a first subsetof the code blocks of a predefined group and a second TFP value for aremainder of the code blocks of the predefined group, wherein the firstand second TFP values are different.
 64. A method implemented in asecond communication node for transmitting a stream of code blocks to afirst communication node, comprising: processing the code blocks inaccordance with at least one transport format parameter (TFP); groupingthe processed code blocks into predefined groups and associating eachcode block or each predefined group of code blocks with a check value;transmitting the predefined groups of code blocks; receiving from thefirst communication node an acknowledgment in respect of one of thepredefined groups of transmitted code blocks; and in response to anegatively valued acknowledgment, retransmitting said predefined groupof transmitted code blocks, wherein said processing includes applying afirst TFP value for a first subset of the code blocks of a predefinedgroup and applying a second TFP value for a remainder of the code blocksof the predefined group, wherein the first and second TFP values aredifferent.
 65. A non-transitory computer readable storage medium of afirst communication node storing a computer program for receiving codeblocks over an acknowledged connection to a second communication node,the computer program comprising instructions that, when executed by atleast one processor of the first communication node, cause the firstcommunication node to: receive a predefined group of code blocks fromthe second communication node, wherein each code block of the predefinedgroup or the predefined group as a whole is associated with a checkvalue enabling error detection; process the received code blocks inaccordance with at least one transport format parameter (TFP); detecterrors in the received code blocks using the check value associated withthe predefined group as a whole or check values for respective codeblocks of the predefined group; transmit to the second communicationnode an acknowledgment indicating whether at least one error wasdetected in the predefined group; and apply a first TFP value for afirst subset of the code blocks of a predefined group and a second TFPvalue for a remainder of the code blocks of the predefined group,wherein the first and second TFP values are independent.
 66. Anon-transitory computer readable storage medium storing a computerprogram for transmitting a stream of code blocks over an acknowledgedconnection to a first communication node, the computer programcomprising instructions that, when executed by at least one processor ofa second communication node, cause the second communication node to:process the code blocks in accordance with at least one transport formatparameter (TFP), group the processed code blocks into predefined groupsof code blocks and associate each code block of a respective predefinedgroup or each respective predefined group as a whole with at least onecheck value; transmit the predefined groups of code blocks; receive fromthe first communication node an acknowledgment corresponding to one ofthe predefined groups of transmitted code blocks; cause retransmissionof said predefined group of transmitted code blocks in response to anegatively valued acknowledgment; and process a first subset of the codeblocks of a predefined group in accordance with a first TFP value and toprocess a remainder of the code blocks of the predefined group inaccordance with a second TFP value, which is independent of the firstTFP value.